Higher plasma levels of thymosin-α1 are associated with a lower waning of humoral response after COVID-19 vaccination: an eight months follow-up study in a nursing home

Immune modulation via dendritic cells by the effect of Thymosin-alpha-1 on immune synapse in HCMV infection

Tα1 (Thymosin-alpha-1) is a thymus-derived hormone that has been demonstrated to be effective on diverse immune cell subsets. The objective of this study was to determine the in vitro immunomodulatory effect of Tα1 in human cytomegalovirus (HCMV) infection. Dendritic cells (DCs) were isolated from peripheral blood mononuclear cells (PBMCs) by negative selection and cultured in the presence or absence of Tα1. The immunophenotyping of DCs was characterised by multiparametric flow cytometry assessing CD40, CD80, TIM-3 and PDL-1 markers, as well as intracellular TNFα production. Then, autologous CD4+ or CD8+ T-Lymphocytes (TLs) isolated by negative selection from PBMCs were co-cultured with DCs previously treated with Tα1 in the presence or absence of HCMV. Intracellular TNFα, IFNγ, IL-2 production, CD40-L and PD-1 expression were assessed through immunophenotyping, and polyfunctionality in total TLs and memory subsets were evaluated. The results showed that Tα1 increased CD40, CD80, TIM-3 and TNFα intracellular production while decreasing PDL-1 expression, particularly on plasmacytoid dendritic cells (pDCs). Therefore, Tα1 modulated the production of TNFα, IFNγ and IL-2 in both total and memory subsets of CD4+ and CD8+ TLs by upregulating CD40/CD40-L and downregulating PDL-1/PD-1 expression. Our study concludes that Tα1 enhances antigen-presenting capacity of DCs, improves TLs responses to HCMV infection, and enhances the polyfunctionality of CD8+ TLs. Consequently, Tα1 could be an alternative adjuvant for use in therapeutic cell therapy for immunocompromised patients.

Performance of SARS COV-2 IgG Anti-N as an Independent Marker of Exposure to SARS COV-2 in an Unvaccinated West African Population

Determination of previous SARS-COV-2 infection is hampered by the absence of a standardized test. The marker used to assess previous exposure is IgG antibody to the nucleocapsid (IgG anti-N), although it is known to wane quickly from peripheral blood. The accuracies of seven antibody tests (virus neutralization test, IgG anti-N, IgG anti-spike [anti-S], IgG anti-receptor binding domain [anti-RBD], IgG anti-N + anti-RBD, IgG anti-N + anti-S, and IgG anti-S + anti-RBD), either singly or in combination, were evaluated on 502 cryopreserved serum samples collected before the COVID-19 vaccination rollout in Kumasi, Ghana. The accuracy of each index test was measured using a composite reference standard based on a combination of neutralization test and IgG anti-N antibody tests. According to the composite reference, 262 participants were previously exposed; the most sensitive test was the virus neutralization test, with 95.4% sensitivity (95% CI: 93.6-97.3), followed by 79.0% for IgG anti-N + anti-S (95% CI: 76.3-83.3). The most specific tests were virus neutralization and IgG anti-N, both with 100% specificity. Viral neutralization and IgG anti-N + anti-S were the overall most accurate tests, with specificity/sensitivity of 100/95.2% and 79.0/92.1%, respectively. Our findings indicate that IgG anti-N alone is an inadequate marker of prior exposure to SARS COV-2 in this population. Virus neutralization assay appears to be the most accurate assay in discerning prior infection. A combination of IgG anti-N and IgG anti-S is also accurate and suited for assessment of SARS COV-2 exposure in low-resource settings.